Re: [Qemu-devel] [PATCH v3] Support 'help' as a synonym for '?' in command line options

[Anthony Liguori]

Peter Maydell <address@hidden> writes:

> For command line options which permit '?' meaning 'please list the
> permitted values', add support for 'help' as a synonym, by abstracting
> the check out into a helper function.
>
> This change means that in some cases where we were being lazy in
> our string parsing, "?junk" will now be rejected as an invalid option
> rather than being (undocumentedly) treated the same way as "?".
>
> Update the documentation to use 'help' rather than '?', since '?'
> is a shell metacharacter and thus prone to fail confusingly if there
> is a single character filename in the current working directory and
> the '?' has not been escaped. It's therefore better to steer users
> towards 'help', though '?' is retained for backwards compatibility.
>
> We do not, however, update the output of the system emulator's -help
> (or any documentation autogenerated from the qemu-options.hx which
> is the source of the -help text) because libvirt parses our -help
> output and will break. At a later date when QEMU provides a better
> interface so libvirt can avoid having to do this, we can update the
> -help text too.
>
> Signed-off-by: Peter Maydell <address@hidden>

Applied. Thanks.

Regards,

Anthony Liguori

> ---
> Changes v1->v2:
>  * dropped the changes to -help text to avoid breaking libvirt
> Changes v2->v3:
>  * call out in the commit message that we've tightened up the
>    parsing so '?junk' is now rejected rather than treated like '?'
>  * add a TODO comment to qemu-options.hx about updating the help text
>    when we are able to
>  * drop a reindent of a comment we only did to placate checkpatch
>  * add 'help' support to "-device devicename,help" (required the
>    introduction of a new qemu_opt_has_help_opt() function)
>  * note that '?' is deprecated in is_help_option documentation.
>
>  arch_init.c       |    4 ++--
>  blockdev.c        |   10 +++++-----
>  bsd-user/main.c   |    4 ++--
>  hw/mips_jazz.c    |    2 +-
>  hw/qdev-monitor.c |    4 ++--
>  hw/watchdog.c     |    2 +-
>  linux-user/main.c |    4 ++--
>  net.c             |    3 ++-
>  qemu-common.h     |   18 ++++++++++++++++++
>  qemu-doc.texi     |    2 +-
>  qemu-ga.c         |    2 +-
>  qemu-img.c        |    4 ++--
>  qemu-option.c     |   12 ++++++++++++
>  qemu-option.h     |   12 ++++++++++++
>  qemu-options.hx   |    4 ++++
>  qemu-timer.c      |    2 +-
>  vl.c              |    4 ++--
>  17 files changed, 70 insertions(+), 23 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index 26f30ef..60823ba 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -680,7 +680,7 @@ void select_soundhw(const char *optarg)
>  {
>      struct soundhw *c;
>  
> -    if (*optarg == '?') {
> +    if (is_help_option(optarg)) {
>      show_valid_cards:
>  
>          printf("Valid sound card names (comma separated):\n");
> @@ -688,7 +688,7 @@ void select_soundhw(const char *optarg)
>              printf ("%-11s %s\n", c->name, c->descr);
>          }
>          printf("\n-soundhw all will enable all of the above\n");
> -        exit(*optarg != '?');
> +        exit(!is_help_option(optarg));
>      }
>      else {
>          size_t l;
> diff --git a/blockdev.c b/blockdev.c
> index 3d75015..8669142 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -398,11 +398,11 @@ DriveInfo *drive_init(QemuOpts *opts, int 
> default_to_scsi)
>  #endif
>  
>      if ((buf = qemu_opt_get(opts, "format")) != NULL) {
> -       if (strcmp(buf, "?") == 0) {
> -           error_printf("Supported formats:");
> -           bdrv_iterate_format(bdrv_format_print, NULL);
> -           error_printf("\n");
> -           return NULL;
> +        if (is_help_option(buf)) {
> +            error_printf("Supported formats:");
> +            bdrv_iterate_format(bdrv_format_print, NULL);
> +            error_printf("\n");
> +            return NULL;
>          }
>          drv = bdrv_find_whitelisted_format(buf);
>          if (!drv) {
> diff --git a/bsd-user/main.c b/bsd-user/main.c
> index cd33d65..095ae8e 100644
> --- a/bsd-user/main.c
> +++ b/bsd-user/main.c
> @@ -681,7 +681,7 @@ static void usage(void)
>             "-g port           wait gdb connection to port\n"
>             "-L path           set the elf interpreter prefix (default=%s)\n"
>             "-s size           set the stack size in bytes (default=%ld)\n"
> -           "-cpu model        select CPU (-cpu ? for list)\n"
> +           "-cpu model        select CPU (-cpu help for list)\n"
>             "-drop-ld-preload  drop LD_PRELOAD for target process\n"
>             "-E var=value      sets/modifies targets environment 
> variable(s)\n"
>             "-U var            unsets targets environment variable(s)\n"
> @@ -825,7 +825,7 @@ int main(int argc, char **argv)
>              qemu_uname_release = argv[optind++];
>          } else if (!strcmp(r, "cpu")) {
>              cpu_model = argv[optind++];
> -            if (strcmp(cpu_model, "?") == 0) {
> +            if (is_help_option(cpu_model)) {
>  /* XXX: implement xxx_cpu_list for targets that still miss it */
>  #if defined(cpu_list)
>                      cpu_list(stdout, &fprintf);
> diff --git a/hw/mips_jazz.c b/hw/mips_jazz.c
> index bf1b799..db927f1 100644
> --- a/hw/mips_jazz.c
> +++ b/hw/mips_jazz.c
> @@ -239,7 +239,7 @@ static void mips_jazz_init(MemoryRegion *address_space,
>              dp83932_init(nd, 0x80001000, 2, get_system_memory(), rc4030[4],
>                           rc4030_opaque, rc4030_dma_memory_rw);
>              break;
> -        } else if (strcmp(nd->model, "?") == 0) {
> +        } else if (is_help_option(nd->model)) {
>              fprintf(stderr, "qemu: Supported NICs: dp83932\n");
>              exit(1);
>          } else {
> diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
> index 7915b45..b22a37a 100644
> --- a/hw/qdev-monitor.c
> +++ b/hw/qdev-monitor.c
> @@ -138,13 +138,13 @@ int qdev_device_help(QemuOpts *opts)
>      ObjectClass *klass;
>  
>      driver = qemu_opt_get(opts, "driver");
> -    if (driver && !strcmp(driver, "?")) {
> +    if (driver && is_help_option(driver)) {
>          bool show_no_user = false;
>          object_class_foreach(qdev_print_devinfo, TYPE_DEVICE, false, 
> &show_no_user);
>          return 1;
>      }
>  
> -    if (!driver || !qemu_opt_get(opts, "?")) {
> +    if (!driver || !qemu_opt_has_help_opt(opts)) {
>          return 0;
>      }
>  
> diff --git a/hw/watchdog.c b/hw/watchdog.c
> index a42124d..b52aced 100644
> --- a/hw/watchdog.c
> +++ b/hw/watchdog.c
> @@ -55,7 +55,7 @@ int select_watchdog(const char *p)
>      QemuOpts *opts;
>  
>      /* -watchdog ? lists available devices and exits cleanly. */
> -    if (strcmp(p, "?") == 0) {
> +    if (is_help_option(p)) {
>          QLIST_FOREACH(model, &watchdog_list, entry) {
>              fprintf(stderr, "\t%s\t%s\n",
>                       model->wdt_name, model->wdt_description);
> diff --git a/linux-user/main.c b/linux-user/main.c
> index a0ab8e8..25eaa11 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -3140,7 +3140,7 @@ static void handle_arg_uname(const char *arg)
>  static void handle_arg_cpu(const char *arg)
>  {
>      cpu_model = strdup(arg);
> -    if (cpu_model == NULL || strcmp(cpu_model, "?") == 0) {
> +    if (cpu_model == NULL || is_help_option(cpu_model)) {
>          /* XXX: implement xxx_cpu_list for targets that still miss it */
>  #if defined(cpu_list_id)
>          cpu_list_id(stdout, &fprintf, "");
> @@ -3231,7 +3231,7 @@ struct qemu_argument arg_table[] = {
>      {"s",          "QEMU_STACK_SIZE",  true,  handle_arg_stack_size,
>       "size",       "set the stack size to 'size' bytes"},
>      {"cpu",        "QEMU_CPU",         true,  handle_arg_cpu,
> -     "model",      "select CPU (-cpu ? for list)"},
> +     "model",      "select CPU (-cpu help for list)"},
>      {"E",          "QEMU_SET_ENV",     true,  handle_arg_set_env,
>       "var=value",  "sets targets environment variable (see below)"},
>      {"U",          "QEMU_UNSET_ENV",   true,  handle_arg_unset_env,
> diff --git a/net.c b/net.c
> index dbca77b..32ca50e 100644
> --- a/net.c
> +++ b/net.c
> @@ -691,8 +691,9 @@ int qemu_show_nic_models(const char *arg, const char 
> *const *models)
>  {
>      int i;
>  
> -    if (!arg || strcmp(arg, "?"))
> +    if (!arg || !is_help_option(arg)) {
>          return 0;
> +    }
>  
>      fprintf(stderr, "qemu: Supported NIC models: ");
>      for (i = 0 ; models[i]; i++)
> diff --git a/qemu-common.h b/qemu-common.h
> index d26ff39..dd91912 100644
> --- a/qemu-common.h
> +++ b/qemu-common.h
> @@ -136,6 +136,24 @@ int qemu_main(int argc, char **argv, char **envp);
>  void qemu_get_timedate(struct tm *tm, int offset);
>  int qemu_timedate_diff(struct tm *tm);
>  
> +/**
> + * is_help_option:
> + * @s: string to test
> + *
> + * Check whether @s is one of the standard strings which indicate
> + * that the user is asking for a list of the valid values for a
> + * command option like -cpu or -M. The current accepted strings
> + * are 'help' and '?'. '?' is deprecated (it is a shell wildcard
> + * which makes it annoying to use in a reliable way) but provided
> + * for backwards compatibility.
> + *
> + * Returns: true if @s is a request for a list.
> + */
> +static inline bool is_help_option(const char *s)
> +{
> +    return !strcmp(s, "?") || !strcmp(s, "help");
> +}
> +
>  /* cutils.c */
>  void pstrcpy(char *buf, int buf_size, const char *str);
>  void strpadcpy(char *buf, int buf_size, const char *str, char pad);
> diff --git a/qemu-doc.texi b/qemu-doc.texi
> index 84dad19..a41448a 100644
> --- a/qemu-doc.texi
> +++ b/qemu-doc.texi
> @@ -2390,7 +2390,7 @@ Set the x86 elf interpreter prefix 
> (default=/usr/local/qemu-i386)
>  @item -s size
>  Set the x86 stack size in bytes (default=524288)
>  @item -cpu model
> -Select CPU model (-cpu ? for list and additional feature selection)
> +Select CPU model (-cpu help for list and additional feature selection)
>  @item -ignore-environment
>  Start with an empty environment. Without this option,
>  the initial environment is a copy of the caller's environment.
> diff --git a/qemu-ga.c b/qemu-ga.c
> index 8199da7..f1a39ec 100644
> --- a/qemu-ga.c
> +++ b/qemu-ga.c
> @@ -736,7 +736,7 @@ int main(int argc, char **argv)
>              break;
>          case 'b': {
>              char **list_head, **list;
> -            if (*optarg == '?') {
> +            if (is_help_option(optarg)) {
>                  list_head = list = qmp_get_command_list();
>                  while (*list != NULL) {
>                      printf("%s\n", *list);
> diff --git a/qemu-img.c b/qemu-img.c
> index 80cfb9b..b866f80 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -350,7 +350,7 @@ static int img_create(int argc, char **argv)
>          img_size = (uint64_t)sval;
>      }
>  
> -    if (options && !strcmp(options, "?")) {
> +    if (options && is_help_option(options)) {
>          ret = print_block_option_help(filename, fmt);
>          goto out;
>      }
> @@ -744,7 +744,7 @@ static int img_convert(int argc, char **argv)
>      /* Initialize before goto out */
>      qemu_progress_init(progress, 2.0);
>  
> -    if (options && !strcmp(options, "?")) {
> +    if (options && is_help_option(options)) {
>          ret = print_block_option_help(out_filename, out_fmt);
>          goto out;
>      }
> diff --git a/qemu-option.c b/qemu-option.c
> index 8334190..27891e7 100644
> --- a/qemu-option.c
> +++ b/qemu-option.c
> @@ -529,6 +529,18 @@ const char *qemu_opt_get(QemuOpts *opts, const char 
> *name)
>      return opt ? opt->str : NULL;
>  }
>  
> +bool qemu_opt_has_help_opt(QemuOpts *opts)
> +{
> +    QemuOpt *opt;
> +
> +    QTAILQ_FOREACH_REVERSE(opt, &opts->head, QemuOptHead, next) {
> +        if (is_help_option(opt->name)) {
> +            return true;
> +        }
> +    }
> +    return false;
> +}
> +
>  bool qemu_opt_get_bool(QemuOpts *opts, const char *name, bool defval)
>  {
>      QemuOpt *opt = qemu_opt_find(opts, name);
> diff --git a/qemu-option.h b/qemu-option.h
> index 951dec3..ca72986 100644
> --- a/qemu-option.h
> +++ b/qemu-option.h
> @@ -107,6 +107,18 @@ struct QemuOptsList {
>  };
>  
>  const char *qemu_opt_get(QemuOpts *opts, const char *name);
> +/**
> + * qemu_opt_has_help_opt:
> + * @opts: options to search for a help request
> + *
> + * Check whether the options specified by @opts include one of the
> + * standard strings which indicate that the user is asking for a
> + * list of the valid values for a command line option (as defined
> + * by is_help_option()).
> + *
> + * Returns: true if @opts includes 'help' or equivalent.
> + */
> +bool qemu_opt_has_help_opt(QemuOpts *opts);
>  bool qemu_opt_get_bool(QemuOpts *opts, const char *name, bool defval);
>  uint64_t qemu_opt_get_number(QemuOpts *opts, const char *name, uint64_t 
> defval);
>  uint64_t qemu_opt_get_size(QemuOpts *opts, const char *name, uint64_t 
> defval);
> diff --git a/qemu-options.hx b/qemu-options.hx
> index dc68e15..9277414 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -6,6 +6,10 @@ HXCOMM construct option structures, enums and help message 
> for specified
>  HXCOMM architectures.
>  HXCOMM HXCOMM can be used for comments, discarded from both texi and C
>  
> +HXCOMM TODO : when we are able to change -help output without breaking
> +HXCOMM libvirt we should update the help options which refer to -cpu ?,
> +HXCOMM -driver ?, etc to use the preferred -cpu help etc instead.
> +
>  DEFHEADING(Standard options:)
>  STEXI
>  @table @option
> diff --git a/qemu-timer.c b/qemu-timer.c
> index de98977..062fdf2 100644
> --- a/qemu-timer.c
> +++ b/qemu-timer.c
> @@ -183,7 +183,7 @@ void configure_alarms(char const *opt)
>      char *name;
>      struct qemu_alarm_timer tmp;
>  
> -    if (!strcmp(opt, "?")) {
> +    if (is_help_option(opt)) {
>          show_available_alarms();
>          exit(0);
>      }
> diff --git a/vl.c b/vl.c
> index 9fea320..1fd1114 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2086,7 +2086,7 @@ static QEMUMachine *machine_parse(const char *name)
>          printf("%-20s %s%s\n", m->name, m->desc,
>                 m->is_default ? " (default)" : "");
>      }
> -    exit(!name || *name != '?');
> +    exit(!name || !is_help_option(name));
>  }
>  
>  static int tcg_init(void)
> @@ -3216,7 +3216,7 @@ int main(int argc, char **argv, char **envp)
>       */
>      cpudef_init();
>  
> -    if (cpu_model && *cpu_model == '?') {
> +    if (cpu_model && is_help_option(cpu_model)) {
>          list_cpus(stdout, &fprintf, cpu_model);
>          exit(0);
>      }
> -- 
> 1.7.9.5